1. Field of the Invention
The present invention relates to a rotor position detecting apparatus in a switched reluctance motor (SRM), and more particularly to a rotor position detecting apparatus in SRM for enabling an easy replacement of a printed circuit board (PCB) and photo-interrupters when they are repaired and maintained.
2. Description of the Prior Art
There is a mutual input signal between SRM and PCB in a conventional mode. When power is supplied, the motor starts operation with an input of an angle between a stator pole and a rotor pole in PCB wherein the angle indicates a rotor position.
Even though there have been a few rotor position detecting sensors, such as hall sensor, encoder and photo-interrupter, only photo-interrupter will be specifically described hereinafter. As shown in FIGS. 1 and 2, the conventional SRM comprises a housing screwed at a circular supporting board (10) and a circulating shaft (30) being connected to the circular supporting board (10) by bearings (40) for simultaneous rotation. At a predetermined distance from the inner wall of stators (50) attached into a housing (20) is a rotor (60) which is designed to drive simultaneously along with the circulating shaft (30).
On the other hand, a rotor position detecting apparatus (70) is installed at an inner wall of the housing (20) and at an outer wall of the circulating shaft (30) to detect the position of the rotor (60). The position detecting apparatus (70) includes a PCB (71) that is closely placed at a side wall of the housing (20) coaxially with the circulating shaft (30), and photo-interrupters (72) with a U-shaped sensing part (72a) at an angle within a certain radius from the center of PCB (71).
In addition, there are a fixing member (73) screwed to drive simultaneously with the circulating shaft (30) and a sensor disc (74) screwed at a side wall of the fixing member (73) with a folded part (74a) perpendicularly disposed at a predetermined angular interval. Position of the folded part (74a) of the sensor disc (74) is detected by the sensing part (72a) of the photo-interrupters (72) Reference numeral 21 designates a ventilator (i.e., a hole) placed at a predetermined angle toward a periphery of the housing (20).
When power is supplied to the PCB (71), as described above, the conventional SRM serves to detect the position of the rotor (60) with the photo-interrupter (72) by way of the circulating shaft (30), the fixing member (73) and the sensor disc (74), and then to notify the detected position of the rotor to PCB (71) to drive the circulating shaft (30) along with the driving rotor (60).
Thus, the position of the rotor (60) is recognized when the folded part (74a) of the sensor disc is located in the sensing parts (72a) of a plurality of photo-interrupters (72). When PCB or photo-interrupters are repaired and maintained, the supporting board (10) needs to be disconnected from the housing (20), the PCB (71) needs to be unscrewed out of the side wall of the housing (20), and the circulating shaft (30) needs to be disassembled from the housing (20). Accordingly the PCB with photo-interrupters is also disassembled and reassembled with the circulating shaft in the conventional SRM when PCB or photo-interrupters are repaired and maintained. These processes are inconvenient and time-consuming when PCB or photo-interrupters are repaired and maintained. In addition the folded part of the PCB can be bent due to the centrifugal force when a motor of a cleaner, for instance, is spinning fast at its high speed.